Clean up some specs

It is actually wrong to be using the same variable name to denote
arguments and return values which have possibly different types.
This patch corrects this.
Do not return wrong terms unnecessarily
Ensure that edocumentation and the xml file are in sync
[stdlib, kernel] Introduce Unicode support for Erlang source files

Expect modifications, additions and corrections.

There is a kludge in file_io_server and
erl_scan:continuation_location() that's not so pleasing.
[edoc] Introduce Unicode support for source files
[erl_docgen] Update due to introduction of Unicode
[syntax_tools] Introduce Unicode support for Erlang source files

Not complete.
Unicode in wild attribute doesn't work.
No support for Unicode regarding Igor stubs.
Update primary bootstrap
[erl_docgen] Use DejaVu fonts when generating PDF

A few examples in lib/stdlib/doc/src/unicode_usage.xml make use of
Cyrillic characters.
[test_server] Add Unicode support to module listing

Code written by Siri Hansen.
[tools] Add Unicode support for Cover

Code written by Siri Hansen.
Correct bugs in the old shell (user.erl)
Clean up some of the Unicode documentation
Improve and correct contracts and types of the IO modules
Make sure the Erlang shell prompt can handle Unicode
Remote the file esyntax.yrl
Merge branch 'hb/parsetools/remove_esyntax/OTP-10660'

* hb/parsetools/remove_esyntax/OTP-10660:
  Remote the file esyntax.yrl
Merge branch 'ks/kernel/dist_util-minor-fix/OTP-10662'

* ks/kernel/dist_util-minor-fix/OTP-10662:
  Do not return wrong terms unnecessarily
Merge branch 'ks/stdlib/proplists-spec-cleanup/OTP-10663'

* ks/stdlib/proplists-spec-cleanup/OTP-10663:
  Ensure that edocumentation and the xml file are in sync
  Clean up some specs
[stdlib] Remove documentation of Unicode functions in io_lib

The documentation of some Unicode functions in io_lib was committed by
mistake.